ELWBINSTEM Résumé de rapport

Final Report Summary - ELWBINSTEM (Development of electrochemical water based in-situ TEM and study of platinum based nanoparticles potential- and time-dependent changes)

Rapid growth of population together with our current unsustainable lifestyle requires progressively increasing amounts of energy. In order to find a solution, the governments and industries are investing more and more money to meet these demands and at the same time to find technologies that would be more efficient, therefore lowering the energy consumption. This, however, comes with nature’s restraints and since it is also not realistic to expect from people to make voluntary lifestyle changes and cut down energy consumption our only option to protect the climate and to save the planet in general is to find sustainable solutions for a clean and efficient energy supply and production. Many scientists and technology developers are focusing their interests towards energy conversion, which enables us to transform chemical energy to electricity or to produce molecules that can be stored and later when necessary transformed back to electricity in a nonpolluting way. Two prospective energy cycles are lately being studied intensively: carbon (CO2 to mainly hydrocarbons and also ethanol and propanol in lower amounts and back) and water cycle (H2O to O2 + H2 and back) [N.M. Markovic, Nature Materials 12 (2013) 101]. However, science has met some of its most challenging obstacles exactly in this field. More specifically in the field of Proton Exchange Membrane Fuel Cells (PEM-FC) platinum based nanoparticles still exhibit relatively low efficiencies and poor stability.To accomplish breakthrough in designing new generation of functional nanomaterials, like energy conversion materials in a form of nanoparticles (PEM-FC electrocatalysts), the insight and understanding of quantitative correlation between electrochemical and nanoscale physical characterization data is needed. For efficient correlative analysis both new advanced experimental and new characterization tools need to be developed required, that will enable a direct correlation between the time- and potential-induced changes and working conditions, i.e. electrochemical water based in-situ TEM (ElWBinsTEM). The advanced TEM characterization in aqueous environment can be realized by the use of specialized TEM holders that can maintain the liquid in a closed container, allowing imaging and spectroscopy of samples in liquid media without altering the vacuum of the microscope. The vital part of such holders is electrochemical microfluidic chamber connected to the external potenciostat, isolated from the microscope vacuum by sandwiching it between two silicon chips containing electron transparent membrane SiN windows. It allows direct imaging and spectroscopic analysis of nanomaterials without the conventional TEM without the restriction of working in high-vacuum environment, which requires dry and dehydrated samples. Therefore conventional type of investigation cannot provide an answer to the question whether the surface structure and morphology integrity get disrupted when metallic samples come in contact with either the atmosphere or are kept immersed in the liquid electrolyte under electrochemical potential control. Project proposed to develop advanced electrochemical water based in-situ TEM technique with nanometer resolution and utilize it to study never before seen potential and time dependent in-situ changes in platinum based nanoparticles when used as electrocatalyst. This has the ability to provide a clear explanation of degradation mechanisms and thus lead to solutions of PEM-FC stability problems. The fellow divided his work in two main work packages and 5 milestones that were all successfully achieved: M1.1:. Construction of electrochemical thin-window cell and representation of electrochemistry control in the electrochemical thin-window cell, M1.2:. Obtaining nanometer resolution TEM picture with the electrochemical thin-window cell without the electrolyte, M1.3:. Obtaining TEM picture with the electrochemical thin-window cell with the electrolyte, M2.1:. Obtaining TEM pictures and movies of dealloying of platinum copper nanoparticles and M2.2:. First confrontation of fellows results at the high-level conference with the participation of academic and industry experts (potential collaborations). Main result was clear evidence in a form of nm-scale movies of the effect of electron beam on Pt nanoparticle coarsening together with Pt deposition when not in contact with working electrode. The main socio-economic impact of the project was the contribution to European excellence and European competitiveness and establishment of a fundamental knowledge that will enable future high-quality research and new breakthroughs on the nanoscale in the field of advanced functional nanomaterials like energy conversion materials in a form of nanoparticles and others.Fellow divided his training into four objectives that were also all successfully achieved: (i) to become in-situ TEM expert, (ii) to become electrochemistry in-situ TEM expert, (iii) to reach the level of expertise to train other researchers in the projects topic and (iv) to establish contact with industrial partners for potential collaborations. Furthermore fellow´s career plan is to become the world leading expert in the field of in-situ electrochemical TEM and therefore needs to further improve his own hands-on experience and finally his high ranking research breakthroughs; based on the data obtained through the project at least two of them are planned in the near future. Fellow actively visited many conferences and general public events at institutes and universities, among which 3 were invited talks, where he acknowledged and promoted the Marie-Curie call.Still, it must be noted that the system only partially satisfies the proposed plan and the scientific appetite of the fellow. The biggest concern lies in the high electron beam effects (water radiolysis) and low stability of the reference potential. On the other hand, for the purpose of obtaining high resolution images, it performs well with expectations. Fellows suggestion for future plan is to produce costume made thin-window micro-electro-mechanical systems (MEMS) in order to: stabilize the potential of reference electrode by changing material from platinum to palladium or by making a separate tank with bulk Ag/AgCl reference electrode, lower the window size and increase their number, optimize the sample (nanoparticles) deposition, option of de-wetting for imaging and subsequent wetting to preform electrochemistry, install control over temperature, ect.In addition fellow also invented and applied for the German patent application on new knowledge on noble metal leaching for the purposes of recycling. Together with in-situ TEM expertise all this experience and knowledge gives the fellow great chances for future successful pursuit of other European projects (ERC, Horizon 2020), direct industry collaborations and his academic career.